1. Field of the Invention
The present invention relates to a method of ascertaining the quality of a workpiece while the workpiece is being manufactured and more particularly to a method of testing the quality of a workpiece while removing material from the workpiece by sensing the applied forces to remove the material from the workpiece and utilizing the sensed applied forces to determine whether the workpiece meets predetermined quality standards.
Methods of testing workpieces are well known in the art. These methods include performing quality control measurements after the workpiece has been machined or performing destructive testing on samples of the workpiece to ascertain the quality of a plurality of workpieces. The known methods of performing quality control on a workpiece do not effect the quality of the workpiece as the workpiece is being machined.
2. Prior Art
The Eshghy Pat. No. 4,267,629 entitled Tension Control of Fasteners discloses the method for tensioning a threaded joint by sensing the torque utilized to tighten the joint over various angles of rotation of the nut. The Eshghy patent does not disclose quality control of mechanical assemblies other than threaded fasteners and has not been used for quality control of a workpiece which is being machined. The Cutler Pat. No. 3,698,268, discloses a Numerical Control System for Interrupted Cutting Conditions which includes a transistor which generates an electrical signal proportional to the force being exerted by the cutter. The force signal is compared with a preset value which is equal to the minimum force exerted by the cutter when it is in contact with the workpiece. The signals are used to indicate whether the cutter is either in contact with the workpiece, out of contact with the workpiece or performing an intermittant or interrupted cut such as occurs when the workpiece is out of round. These signals are used to provide control signals to the spindle to control the spindle speed and rate of feed of the cutter relative to the spindle. Cutler does not disclose performing a quality control operation on the workpiece as it is machined.
The Watanabe et al Pat. No. 3,834,615, discloses a machine tool control system wherein the reaction force on the cutting tool is detected in the form of three components, i.e. a backing force component, a feeding force component and a main force component. The sensed force values are then compared with corresponding reference values to detect abnormal conditions of the cutting tool. Watanabe et al also does not disclose a method of controlling the quality of the workpiece while it is machined. The Hoffman Pat. No. 3,878,982, discloses an Automatic Target Management Method and System which automatically and continuously senses dispersion of a measured property of process material and automatically controls the process to maintain a given fraction of the processed material on the proper side of the limiting value. Johnstone Pat. No. 3,882,305, discloses a diagnostic communication system for a computer controlled machine tool. The Johnstone patent is directed to a method of performing preventative maintenance on a computer controlled machine by collecting signals derived from the machine tool and analyzing the machines performance by comparing the parameters represented by the collected signals with design parameters for the machine. However, Johnstone does not disclose utilizing the collected perimeters to control the quality of a workpiece being machined. Tsukada et al Pat. No. 4,090,403, discloses an Apparatus For Judging The Useful Life of Tools but does not disclose a quality control operation for controlling the quality of a machined workpiece.